In high-speed and/or high-integration semiconductor devices, metal wiring may be finer and/or may have multiple layers. As widths of metal wiring are reduced, signal delay may occur due to the resistance and the capacitance of the metal wiring. To reduce signal delay, Copper having a low resistance may be employed as part of metal wiring.
Copper is relatively difficult to etch. Copper wiring may be formed through a damascene process, which may not require etching of Copper. A damascene process may include at least one of: forming a trench; forming a Copper layer inside the trench; and/or performing chemical mechanical polishing.
Copper may diffuse into other layers. A barrier layer may be formed inside a trench before filling the trench with Copper. A barrier layer may be formed of Tantalum (Ta). A Tantalum (Ta) film may not prevent diffusion of Copper. A barrier layer may be formed with Tantalum Nitride (TaN), which may prevent Copper diffusion better than a Tantalum (Ta) film. A Tantalum Nitride (TaN) film may have a relatively low adhesive strength with Copper.
A barrier layer may be formed with a dual film of Tantalum (Ta) and Tantalum Nitride (TaN). A dual fim of Tantalum (Ta) and Tantalum Nitride (TaN) may be both an adequate diffusion barrier and have adequate adhesive strength with Copper. A dual-film barrier layer may be formed by physical vapor deposition (PVD) and/or atomic layer deposition (ALD).
When a dual-film barrier layer is formed by PVD, overhanging may occur resulting in blockage of a via. Overhanging may occur if an aspect ratio (e.g. a ratio of depth to width) of a via is relatively large, which may lead to improper formation of a barrier layer.
When a dual-film barrier layer is formed by ALD, a TaN film and a Ta film may be formed by using different precursors, which may make the formation process relatively complicated. During ALD, since Carbon (C) and Oxygen (O) may be in a TaN film, the resistivity of the TaN film may become relatively large.